Genetics of Aggregation Pattern Mutations in the Cellular Slime Mould Dictyostelium discoideum

Abstract

A class of aggregation pattern mutants called streamers were isolated from D. discoideum and analyzed genetically. The streamer phenotype is the formation of very large streams of centripetally moving amebae which are collected from abnormally large territories during the aggregation phase of this organism. Such mutants do not show the pleiotropic developmental defects seen with most other classes of aggregation mutants, and after the abnormal aggregation phase they develop into normally differentiated stalk cells and spores. Twenty-four haploid streamers were isolated and assigned to 7 complementation groups, stmA to stmG, after selecting diploids formed between pairs of the mutants. The complementation loci were assigned to the following linkage groups using parasexual genetic techniques: stmA and stmF, linkage group VII; stmB, stmD and stmG, linkage group II; stmC and stmE, linkage group III. Use was made of a new temperature sensitive for growth marker, tsgK21, which was assigned to linkage group VII. The total number of complementation groups giving the streamer phenotype is estimated from statistical calculation, based on the frequency of allelism, to be 7-9.